I have both a roof mounted and a carry out. Prior owner paid for the roof dome. I only have one TV in the coach so can't comment based on experience concerning using the domed antennas to feed independent receivers. Both the domes have two coax outputs to support two receivers but I don't know how the dome would react to conflicting demands for signal from two different satellites. I've removed the domes and watched the antenna shift between satellites as I change channels.
What I will comment about is the roof mount and carry out. Most of my camping is in government parks (Mid Atlantic region) and the roof dome is blocked by trees and hills 80 to 90% of the time. The carry out I have gives me much more flexibility to find an opening where it can see the required satellites. I have a roll of 200' of coax/power cable and have used all of it a few times without a problem. I've also tried the roof dome while going down the road. Hit and miss with a lot of signal lose due to obstructions. Suspect when and if I ever get west of the Mississippi River and on the Great Plains it would probably work great.
Highly recommend a carry out over a permanent roof mount. Besides one less place for water to get in thru the roof and when you change rigs you can move it to the new coach. I've also used the carry out during our group rally around community big screen someone supplied.